relative paths to tests

tests/PyPlamlTest.py

 import os
+import pathlib
 import unittest
-from glob import glob
 
 from pyplaml import *
 
@@ -8,8 +8,10 @@ from pyplaml import *
 # noinspection PyBroadException
 class PyPlamlTest(unittest.TestCase):
     def setUp(self):
+        puml_files = pathlib.Path(__file__).parent.parent / 'examples' / 'plantuml'
+
         self.parser = PUMLParser()
-        self.examples_sorted = sorted(glob("../examples/plantuml/*.puml"))
+        self.examples_sorted = sorted(puml_files.glob("*.puml"))
 
     def test_lexer(self):
         for example_file in self.examples_sorted:
@@ -23,9 +25,11 @@ class PyPlamlTest(unittest.TestCase):
                 self.assertTrue(False, f"Parser exception in {example_file}")
 
     def test_drawing(self):
+        main_script = Path(__file__).parent.parent / 'main.py'
+
         for e in self.examples_sorted:
             self.assertEqual(
-                os.system("python ../main.py " + e),
+                os.system(f"python {main_script} {e}"),
                 0,
                 f"Drawing \"{e}\" failed"
             )